Concrete Block Weight by Size

Do not calculate a hollow block’s weight from its full external dimensions as though it were solid concrete; actual net concrete volume is significantly less than gross volume.

Standard 8x8x16 Concrete Block Weight

This is the most commonly searched CMU weight query. Documented examples include a lightweight hollow unit at 30 lb (premier concrete, Lowe’s listing), a lightweight unit at 37 lb (a different lightweight product line), and normal-weight units at 39 lb (Kingston Block, Basalite) and 39.5 lb (a separate normal-weight product listing). A particular supplier’s 39-lb normal-weight block is not inconsistent with another supplier offering a somewhat lighter block of the same nominal size; both can comply with ASTM C90 under their respective density classifications.

Important Weight Qualifications

CMU weights vary by manufacturer, concrete density, internal geometry, moisture content, and product type. The values in this chart are approximate and representative rather than precise universal standards; always confirm exact product weight with the manufacturer’s technical data sheet before ordering, lifting, or structural calculations.

• External dimensions: Nominal size sets the overall envelope, but not the weight directly.
• Concrete density: Oven-dry density of the concrete material itself, measured in lb/ft³.
• Internal voids: Core size and number reduce net concrete volume.
• Face-shell and web thickness: Thicker shells and webs increase net concrete volume and weight.
• Aggregate type: Natural stone, expanded shale, clay, or slate aggregates have different particle densities.
• Moisture content: As-delivered weight differs from oven-dry weight.
• Specialty configuration: Bond-beam, lintel, and other specialty units have different net volumes than standard two-core block.

Identical nominal dimensions do not imply identical weight; two 8x8x16-inch blocks from different manufacturers or density classes can differ by 25 percent or more.

These are all documented published values for genuine products, not calculated estimates. The variation between 30 and 39.5 pounds for the same nominal size illustrates why manufacturer-specific data, not a single universal figure, should govern procurement and structural weight calculations.

Nominal 4x8x16-inch partition blocks are commonly used where wall thickness is limited, such as interior partitions and furring applications. Representative industry ranges place these units around 18-29 lb depending on density class, though structural suitability should always be verified separately from weight comparison. Nominal 6x8x16-inch blocks fall in an intermediate range, around 24-36 lb, and represent a common compromise between the handling advantages of thinner units and the structural or fire-rating benefits of thicker walls.

Nominal 10x8x16 and 12x8x16-inch CMUs are used where greater wall thickness, higher fire ratings, or increased grouted reinforcement capacity is required. Representative industry ranges place 10-inch units around 34-48 lb and 12-inch units around 38-54 lb depending on density class, though larger units can have different face-shell and web arrangements than smaller units, so weight does not scale in strict proportion to nominal width. Published manufacturer data for the specific product should be used rather than scaling an 8-inch block’s weight purely by nominal width ratio.

Converted values are rounded to one decimal place. Distinguish exact unit conversions from approximate source weights when precision matters.

• Net concrete volume: The actual volume of concrete material in the unit.
• Gross external volume: The volume of the unit’s full outside envelope, including hollow cores.
• Face shells: The solid outer walls of a hollow unit.
• Internal webs: Solid cross-members connecting the face shells.
• Hollow cores: Void spaces within the unit reducing net volume and weight.

Using only outside dimensions significantly overestimates the weight of a hollow unit, since a substantial portion of the gross volume is void space. A fully grouted hollow block is also not identical in weight or construction to a manufactured solid unit; the grout fills the cores after installation, while a solid unit is cast with concrete throughout at manufacture.

Density is mass per unit volume; weight is the total mass of a specific object. ASTM C140 testing determines oven-dry concrete density using the actual net material volume, not the gross external volume as if the unit were solid. CMHA’s assembly-weight calculations use representative densities of 103, 115, and 135 lb/ft³ for lightweight, medium-weight, and normal-weight units respectively; these are estimating assumptions used for wall dead-load calculations, not the ASTM classification boundaries themselves.

Natural aggregates such as sand and crushed stone generally produce denser, heavier concrete. Manufactured lightweight aggregates, including expanded shale, expanded clay, and expanded slate, reduce particle density and produce lighter concrete for a given volume. Blended aggregates fall between these extremes.

Common nominal 8x8x16-inch CMUs are typically manufactured to approximately 7 5/8 x 7 5/8 x 15 5/8 inches to accommodate a 3/8-inch mortar joint, subject to the applicable product specification. This actual (specified) size, not the rounded nominal figure, is what determines the unit’s true net concrete volume and therefore its weight. For the complete dimensional inventory across all CMU types, see the Masonry Block Size Chart rather than duplicating that data here.

ASTM C90-24a covers dry-cast hollow and solid loadbearing concrete masonry units, including density classification, material properties, and applicable physical requirements such as compressive strength and absorption limits. ASTM C90 classifies units by the concrete’s density but does not prescribe an identical unit weight for every standard block size; weight depends on the combination of density class and the specific unit’s net concrete volume.

ASTM C140/C140M-26a establishes the sampling and test methods manufacturers and laboratories use to determine unit dimensions, density, absorption, and moisture content. There is an important distinction between weighing a block as received (which includes ambient moisture) and determining its oven-dry density under the applicable test procedure, which dries the specimen to a constant mass before calculating density from net volume.

ASTM C90 covers loadbearing units, while ASTM C129-26 covers nonloadbearing concrete masonry units. Loadbearing classification is a structural product requirement, not a separate universal weight designation. A nonloadbearing block is not necessarily lighter simply because it is nonloadbearing; its weight still depends on the same density-class and geometry factors that govern any CMU.

Specialty shapes require product-specific weights and cannot automatically be estimated by scaling the ordinary two-core CMU chart; consult the manufacturer’s data sheet for each specialty product.

These are wall assembly weights, including mortar bedding, bond beams, and reinforcing steel allowances, not individual block weights. Values assume 100-140 pcf grout density and specific unit densities as stated; the actual assembly weight depends on the specific project’s units, grout spacing, and reinforcement.

Grout substantially increases the dead load of a masonry wall; a fully grouted 8-inch normal-weight wall can weigh over 50 percent more than the same wall left ungrouted. Reinforcing steel, bond beams, mortar type, and actual unit geometry all affect a more detailed estimate beyond this representative reference table.

Use actual net concrete volume when estimating hollow-unit weight; substituting gross external volume as though the unit were solid produces a significant overestimate. A manufacturer-published unit weight is preferable to a calculated estimate for procurement and lifting-equipment planning, since it reflects the actual as-manufactured product rather than idealized geometry. Calculated oven-dry weight also differs from as-delivered weight, which includes ambient moisture absorbed during storage.

Mortar joints are already accounted for in the nominal 8 x 16-inch module used for this calculation. See the Concrete Block Calculator for a full quantity takeoff including openings.

Block-only weight is not complete wall weight; use the wall-weight-per-square-foot tables above (which already include mortar and reinforcement allowances) for structural dead-load estimating instead of summing block weight alone.

Using the appropriate assembly weight in lb/ft² is generally more useful for structural dead-load estimating than multiplying block count by unit weight alone, since the assembly figure already accounts for mortar and typical reinforcement allowances.

Do not assume all manufacturers use identical pallet quantities; one documented supplier lists 90 units per pallet for standard 8x8x16 block, but this varies by producer and product line. Add a packaging and pallet-weight allowance to the total block weight for an estimated gross pallet weight, and confirm with the specific supplier before planning delivery or handling equipment.

Project quantity, pallet weights, vehicle payload capacity, delivery site access, and unloading equipment all affect material logistics. A theoretical block-weight estimate does not establish a vehicle’s legal payload or a crane or forklift’s rated lifting capacity; confirm actual equipment ratings and delivery logistics with the supplier and site superintendent separately from the weight chart.

Lightweight and normal-weight blocks differ in repetitive handling effort, since masons lift each unit individually throughout a project. A lower unit weight can reduce handling fatigue over a full day of laying block, while actual installation productivity also depends on unit size, wall design, project conditions, and crew methods. Avoid presenting a specific universal labor-savings percentage without a defined comparison study.

• Wall dead load: The completed wall’s self-weight, using the assembly weight tables above.
• Floor and roof support: Masonry walls transfer their own weight plus supported loads to the foundation.
• Footing loads: Wall weight contributes to the total load a footing must support.
• Seismic mass: Heavier walls increase seismic demand in high-seismic regions.
• Reinforcement and grout contributions: Add measurably to total dead load, as shown in the grout-condition table above.

For footing sizing based on supported loads, see the Footing Size Chart and confirm soil capacity with the Soil Bearing Capacity Chart; actual footing design requires the complete structural load path and an engineered design, not just wall weight.

CMU density and configuration can influence thermal storage capacity (heat capacity) and acoustical performance (sound transmission). Do not treat unit weight alone as proof of a particular fire-resistance rating, R-value, or sound transmission class; these properties depend on the tested or calculated complete assembly, including grout, finishes, and construction details, not weight in isolation.

1. Identify the block’s exact nominal and actual dimensions.
2. Determine the density classification (lightweight, medium, or normal weight) from the manufacturer.
3. Identify the manufacturer and specific product line.
4. Note the moisture condition (as-delivered vs. oven-dry).
5. Check the supplier’s technical data sheet for published unit weight.
6. Test representative units directly where precise quantities are important, using ASTM C140/C140M procedures for certified results.

1. Identify the wall’s structural function and applicable material specification.
2. Determine the permitted unit size and density classification.
3. Check manufacturer availability and documented unit weight.
4. Calculate complete wall dead load where required.
5. Account for grout and reinforcement contributions.
6. Verify delivery and handling arrangements.

Structural suitability, strength, fire resistance, and other specified performance requirements take precedence over choosing a block solely because it is lighter; weight is one input among several, not the primary selection criterion.